In recent years there has been a tremendous growth in data communications, especially among residential users accessing the global Internet and the World Wide Web. Many of these residential users gain such access through gateway services provided by an internet service provider (ISP).
With the growth in Internet-related data traffic, network service providers (NSPs) have had to seek ways to quickly upgrade network facilities to alleviate congestion and bottlenecks in their networks. The NSPs have begun to deploy asynchronous transfer mode (ATM) technology in the core or backbone of the networks as an efficient and flexible means of carrying the large amounts of data traffic. ATM is also reaching to the edge or access portion of the network where it is being deployed in digital subscriber loop access multiplexers (DSLAM) or access nodes that connect residential users to ISPs through the ATM network.
Packet data communication between ISPs and residential users is supported by the Internet Protocol (IP). In the standard approach for carrying IP traffic over ATM, each connection between a user and an ISP requires a separate virtual circuit (VC). Since switched virtual circuit support in the ATM backbone network is not likely to happen in the short term, these virtual circuits are permanent virtual circuits (PVCs) which need to be present whether the end user is actively connected or simply idle. The number of PVCs required for a large scale network with many users and many possible destinations can be prohibitive to meet and manage. With a standard network trunk (e.g., SONET OC-3 rate) able to support only about 1000 virtual circuits, such a limitation means that a network trunk terminated at the ISP can only support about 1000 potential users.
The above problems are overcome and other advantages achieved with the present invention. According to the invention, data packets from multiple users destined for a particular ISP are multiplexed onto the same virtual circuit. The multiplexing method and apparatus of the present invention provides for more efficient use of virtual circuits in an ATM network. In addition, a network trunk terminated at the ISP can reach more access nodes. As each access node is connected to hundreds of users, a single trunk at the ISP can reach many more than 1000 potential users. Depending on the expected internet access demand from the end users, a much more economical configuration of permanent virtual circuits between ISPs and access nodes can be realized using the principles of the present invention.
Accordingly, the invention provides a method and apparatus for communicating to a destination node over a broadband network from plural users connected to an access node. A virtual circuit is provisioned through the broadband network for connecting the access node to the destination node. Data units are received from plural users at the access node, with each data unit having plural cells. The data units are multiplexed onto the virtual circuit at the access node such that the cells of any one data unit are noninterleaving with the cells of any other data unit on the virtual circuit. In a preferred embodiment, the destination node is a service provider node in an ATM network and the data units are Ethernet protocol data units that comprise plural ATM cells.
According to an aspect of the invention, access to multiple service provider nodes is provided at the same or differing priority levels. Accordingly, a second virtual circuit is provisioned to a second service provider node. Ethernet protocol data units on the first virtual circuit have a first service priority and the second Ethernet protocol data units on the second virtual circuit have a second service priority, the first priority being higher than the second priority, such that the multiplexing step includes preempting ATM cells of the second Ethernet protocol data units with ATM cells of the first Ethernet protocol data units.
According to another aspect of the invention, an access node for communicating to a service provider node over an ATM network from plural users includes at least one line unit for transmitting downstream and receiving upstream Ethernet protocol data units to and from plural users, each Ethernet protocol data unit comprising plural ATM cells, the line unit coupling the ATM cells to and from a communication bus. A trunk unit coupled to the communication bus transmits upstream ATM cells and receives downstream ATM cells to and from the ATM network.
The line unit further includes means for multiplexing the upstream Ethernet protocol data units onto a virtual circuit connecting the access node to the service provider node such that the ATM cells of any one upstream Ethernet protocol data unit are noninterleaving with the ATM cells of any other upstream Ethernet protocol data unit on the virtual circuit. The line unit further includes means for selecting downstream ATM cells from the communication bus that are destined for any of the plural users associated therewith based on a virtual circuit identifier and a PDU address in the data unit. The means for selecting includes means for detecting the start of an Ethernet protocol data unit, means for buffering the ATM cell, means for detecting the PDU address, and means for buffering all ATM cells of the Ethernet protocol data unit for transmission to the user associated with the PDU address.
According to another aspect of the invention, an access node provides multi-destination support to allow users to select among destination service provider nodes.